Factors responsible for abortion

1. Endocrine and metabolic factors -
Luteal phage defect (LPD) results in early miscarriage as implantation and plancental are not supported adequately. Deficient progesterone secretion from corpus luteum or poor endometrial response to progesterone is the cause. Diabetes mellitus when poorly controlled, causes increased miscarriage.

2. Anatomical abnormalities - 
These are related mostly to the second trimester abortions.
- Cervical incompetance.

- Congenital malformation of the uterus is cause of fetal loss.

- Reduced intrauterine volume.

- Increased uterine irritability and contraction.

- Intrauterine adhesions interfere with implantation, placental and fetal growth.

3. Infections -

Infections are accepted causes of late as well as early abortions. Infections could be :

i) Viral :- Rubella, HIV.

ii) Parasitic :- Toxoplasma, malaria.

iii) Bacterial :- Chlamydia, brucella.

4. Immunological disorders

5. Environmental factors

6. Genetic factors

7. Others -

- Maternal medical illness.

- Cyanotic heart disease (CHD).

- Blood group incompatibility.

- Premature rupture of membranes.

- Inherited thrombophilia.

How environmental factor is responsible for abortion

Smoking -
Cigarette smoking increases the risk due to formation of carboxy haemoglobin and decreased oxygen transfer to the fetus. Alcohol consumption should be avoided or minimized during pregnancy.

X-Irradiation and antineoplastic drugs are known to abortion. X-ray exposure is a risk of abortion,
so it is avoided or minimized in the pregnancy period.

Contraceptive agents -
IUD (Intrauterine device) increases the risk whereas oral pill do not.

Drugs, chemicals and noxious agents -
Anaesthetic gases, arsenic, lead, formaldehyde increases the risk.

Miscellaneous - 
Exposure to electro-megnetic radiation from video display terminals does not increase the risk. Woman can safely use hair dyes, watch television and fly in airlines during pregnancy.